Method of bending a long length of a member and bending apparatus for use in such method

ABSTRACT

The method of bending the long length of the member and a bending apparatus which are capable of restraining the occurrence of wrinkles in flanges of the long length of the member, preventing free end sides of the flanges from buckling, and setting and taking out the long length of the member easily in bending a long length of a member in the longitudinal direction, which is approximately L-shaped or U-shaped in cross section and has a platelike bottom portion and flanges installed in a standing manner at the end of the platelike bottom portion, it is to provide. By using an inner forming assembly forming an inner bent shape of the long length of the member, an outer forming assembly having a forming pad being capable of projecting and retracting so as to form an outer bent shape of the long length of the member and die plate being rotatable following the forming pad and a sidewall provided in the longitudinal direction of the outer forming assembly, and by pressing the long length of the member in the outer forming assembly with the inner forming assembly and by doing the ironing of the flanges with the sidewall and the inner forming assembly, the occurrence of wrinkles in flanges is restrained, and free end sides of the flanges is prevented from buckling by extending gradually a bending fulcrum through a retraction of the forming pad and rotations of the die plates. Further, by installing a moving mechanism to the sidewall, setting and taking out the long length of the member is facilitated.

DETAILED DESCRIPTION OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of bending a long length of a member being approximately L-shaped or U-shaped in cross section in the longitudinal direction and a bending apparatus for use in such method.

[0003] 2. Prior Art and Problems to be Resolved by the Invention

[0004] It is difficult to form a long length of a member which is approximately L-shaped or U-shaped in cross section and curved in the direction of the length thereof as a unity, and therefore, in conventional method, such a member is manufactured by dividing a member into a plurality of parts in the longitudinal direction and by welding the bent parts after bending the dividing parts separately. That is, as shown in FIG. 9, a long length of a member having such a shape as described above is manufactured as the whole member by dividing a member into a member 31 not having the bending in the longitudinal direction, a member 32 having a largely bending part in the longitudinal direction and a member 33 having a small bending part in the longitudinal direction, manufacturing parts having these divided shapes separately and welding these manufactured parts. Therefore, to manufacture the long length of the member having such a shape as described above, many steps are required and the manufacturing cost becomes high. Accordingly, to reduce the manufacturing cost of the above-mentioned long length of the member, it is required to research forming as a unity.

[0005] Currently, as a method of forming a long length of a member as a unity, there are methods utilizing draw forming or bending divided into two processes, the bending of the direction of cross section and the bending of the longitudinal direction. However, in draw forming, draw forming must be carried out using steel plate having a dimension sufficiently larger than the steel plate to which completed products is spread because steel plate must be restrained in machining, and excessive parts must be eliminated by laser cutting or plasma cutting after draw forming. Therefore, there is a defect that material yield decreases in draw forming.

[0006] Further, a forming object of draw forming is usually a thin plate (thickness of 0.6 mm to 2.3 mm), it is said that it is difficult to draw form a thick plate (for example, thickness of 4.5 mm or more). And, if draw forming of the thick plate is performed, the facilities which have the ability of pressing being capable of draw forming the thick plate and the molds with the corresponding high hardness are required, and therefore the cost of equipment required becomes enormous. Accordingly, it is impossible to reduce the manufacturing cost in bending the long length of the member described above by draw forming.

[0007] On the other hand, in a method of bending divided into two processes, a shape in transverse cross section is first formed by the bending of a first process, and then a shape in the longitudinal direction is formed by the bending of a second process. The bending method of the second process is shown in FIG. 10. The bending of the second process is intended to carry out the bending by supporting both ends of the long length of the member by a lower mold 35 forming an outer bent shape of the long length of the member and by pressing a part to be a largely bending part 43 of the platelike bottom portion 41 of the long length of the member by an upper mold 36 forming an inner bent shape of the long length of the member. However, in such a bending method, it is a problem to cause buckling in free end side of the flanges 42 in which the large deformation is produced due to contraction. The occurrence of buckling is remarkable particularly when a long length of a member is bent to a large extent.

[0008] Accordingly, to reduce the manufacturing cost, it is required to research a machining method in which, in a method of bending divided into two processes, buckling does not occur in free end of flange 42 in bending in the longitudinal direction.

[0009] This invention has been invented to resolve the above-mentioned conventional defects and it is an object of the invention to provide a method of bending a long length of a member and a bending apparatus which are capable of preventing a wrinkle from occurring in flanges of a long length of a member due to buckling of free end sides of the flanges in bending the long length of the member in the longitudinal direction, which is approximately L-shaped or U-shaped in cross section and has a platelike bottom portion and flanges installed in a standing manner at the end of the platelike bottom portion. Also an object of the invention is to provide a method of bending a long length of a member and a bending apparatus which are capable of setting and taking out a long length of a member easily in bending described above.

MEANS OF SOLVING THE PROBLEMS AND EFFECTS OF THE INVENTION

[0010] And so, a method of bending a long length of a member of claim 1 is the method of bending, wherein, in a long length of a member which has a platelike bottom portion 1 and flanges 2 installed in a standing manner at the end of the platelike bottom portion 1, free end sides of the flanges 2 shrink and platelike bottom portion 1 sides of the flanges 2 expand, characterized in that, in bending the long length of the member by using an inner forming assembly 20 forming an inner bent shape of the long length of the member and an outer forming assembly 6 forming an outer bent shape of the long length of the member and by pressing the platelike bottom portion 1 in the above-mentioned outer forming assembly 6 with the above-mentioned inner forming assembly 20, the above-mentioned flanges 2 are pressed from both sides thereof between a sidewall 8 of the above-mentioned outer forming assembly 6 and the above-mentioned inner forming assembly 20, respectively, bending is carried out while doing the ironing of the above-mentioned flanges 2 with the above-mentioned sidewall 8 and the above-mentioned inner forming assembly 20.

[0011] And, a bending apparatus for a long length of a member of claim 2 is the bending apparatus for carrying out the bending in which, in a long length of a member having a platelike bottom portion 1 and flanges 2 installed in a standing manner at the end of the platelike bottom portion 1, free end sides of the flanges 2 shrink and platelike bottom portion 1 sides of the flanges 2 expand, including an inner forming assembly 20 forming an inner bent shape of the long length of the member and an outer forming assembly 6 forming an outer bent shape of the long length of the member, bending the long length of the member by pressing the platelike bottom portion 1 in the above-mentioned outer forming assembly 6 with the above-mentioned inner forming assembly 20, characterized in that the above-mentioned flanges 2 are pressed from both sides thereof between a sidewall 8 provided in the above-mentioned outer forming assembly 6 and the above-mentioned inner forming assembly 20, respectively, and the bending is carried out so as to do the ironing of the above-mentioned flanges 2 with the above-mentioned sidewall 8 and the above-mentioned inner forming assembly 20.

[0012] In accordance with the above-mentioned method of bending a long length of a member of claim 1 and the above-mentioned bending apparatus for a long length of a member of claim 2, it is possible to restrain the occurrence of wrinkles effectively, which are going to be produced at flanges 2 due to bending the long length of the member. That is, by pressing the platelike bottom portion 1 of the long length of the member in the outer forming assembly 6 by the inner forming assembly 20, the deformation that free end sides of flanges 2 shrink and platelike bottom portion 1 sides of the flanges 2 expand is produced in the longitudinal direction of the long length of the member. The wrinkles resulting from buckling are going to be produced at flanges 2 due to the deformation. However, since the sidewalls 8 provided in the longitudinal direction of the outer forming assembly 6 press respective flanges 2 against the inner forming assembly 20, and the sidewall 8 and the inner forming assembly 20 do the ironing of the flanges 2, it is possible to restrain the occurrence of wrinkles.

[0013] And, a bending apparatus for a long length of a member of claim 3 has a forming pad 9 and die plates 10 in the longitudinal direction in such a way that an outer forming assembly 6 forms an outer bent shape of the long length of the member, and is characterized in that the above-mentioned forming pad 9 is installed so as to be capable of projecting and retracting by being applied with a force toward the direction of the above-mentioned inner forming assembly 20 by a means 16 of applying a force and the sides of the above-mentioned forming pad 9 of the above-mentioned die plates 10 are installed rotatably following a projection/retraction of the above-mentioned forming pad 9.

[0014] In accordance with the bending apparatus for a long length of a member of claim 3, by pressing the platelike bottom portion 1 of the long length of the member by the inner forming assembly 20, the forming pad 9 retracts and the sides of the forming pad 9 of the die plates 10 are rotated to the direction of a retraction of the forming pad 9, and a bending fulcrum of the long length of the member is extended gradually toward both ends of the long length of the member and a largely bending part 3 is formed gradually. Thereby, since free end sides of the flanges 2 of the largely bending part 3 shrink gradually, it is possible to prevent free end sides of the flanges 2 from buckling effectively.

[0015] Furthermore, as the forming pad 9 retracts, the ironing is applied to each flange 2 of the long length of the member through a side face of the sidewall 8 and the inner forming assembly 20. As the forming pad 9 retracts, the sides of the forming pad 9 of the die plates 10 are rotated to the direction of a retraction of the forming pad 9, and therefore the flanges 2 applied with the ironing is extended gradually toward both ends of the long length of the member and this results in the ironing of the whole flange 2, and so it is possible to restrain the occurrence of wrinkles further.

[0016] The bending apparatus for a long length of a member of claim 4 is characterized in that the bending apparatus have a moving mechanism for moving the sidewalls 8 provided in the longitudinal direction of an outer forming assembly 6 away from flanges 2.

[0017] In accordance with the above-mentioned bending apparatus for a long length of a member of claim 4, when the long length of the member is set to the outer forming assembly 6, the long length of the member may be set to the outer forming assembly 6 easily since the sidewalls 8 position on the outer sides, and when bending, the sidewalls 8 press the flanges 2 against the inner forming assembly 20 and bending is carried out while doing the ironing of the flanges 2 with the sidewall 8 and the inner forming assembly 20, and after bending is completed, the long length of the member may be taken out from the outer forming assembly 6 easily since the sidewalls 8 move away from the flanges 2.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective view illustrating one example of a long length of a member being approximately U-shaped in cross section.

[0019]FIG. 2 shows an outer forming assembly in an embodiment of a bending apparatus for a long length of a member of the present invention and FIGS. 2(a) is a top plan view, (b) is a sectional front elevation view and (c) is a sectional side elevation view.

[0020]FIG. 3 shows an inner forming assembly in an embodiment of a bending apparatus for a long length of a member of the present invention and FIGS. 3(a) is a bottom plan view, (b) is a front elevation view and (c) is a sectional side elevation view.

[0021]FIG. 4 is a view illustrating in stages the method of bending the long length of the member of the present invention and shows a sectional diagrammatic sketch of a machining step at the start of bending, and FIGS. 4(a) is a sectional front elevation diagrammatic sketch and (b) is a sectional side elevation diagrammatic sketch.

[0022]FIG. 5 is a view illustrating in stages the method of bending the long length of the member of the present invention and shows a sectional diagrammatic sketch of a machining step proceeding further than the machining step of FIG. 4, and FIGS. 5(a) is a sectional front elevation diagrammatic sketch and (b) is a sectional side elevation diagrammatic sketch.

[0023]FIG. 6 is a view illustrating in stages the method of bending the long length of the member of the present invention and shows a sectional diagrammatic sketch of a machining step proceeding further than the machining step of FIG. 5, and FIGS. 6(a) is a sectional front elevation diagrammatic sketch and (b) is a sectional side elevation diagrammatic sketch.

[0024]FIG. 7 is a view illustrating in stages the method of bending the long length of the member of the present invention and shows a sectional diagrammatic sketch of a machining step proceeding further than the machining step of FIG. 6, and FIGS. 7(a) is a sectional front elevation diagrammatic sketch and (b) is a sectional side elevation diagrammatic sketch.

[0025]FIG. 8 is a view illustrating in stages the method of bending the long length of the member of the present invention and shows a sectional diagrammatic sketch of a machining step at the end of bending, and FIGS. 8(a) is a sectional front elevation diagrammatic sketch and (b) is a sectional side elevation diagrammatic sketch.

[0026]FIG. 9 is a view illustrating a conventional manufacturing process of the long length of the member being approximately U-shaped in cross section.

[0027]FIG. 10 is a view illustrating the bending in a second process of a conventional method of bending in which the bending of the long length of the member being approximately U-shaped in cross section is divided into two processes.

EMBODIMENTS OF THE INVENTION

[0028] Next, referring to the drawings, there is illustrated in detail specific embodiment of a method of bending a long length of a member and a bending apparatus for a long length of a member of the present invention. The present embodiment shows the method of bending a long length of the member A and the bending apparatus for use in such method as shown in FIG. 1 as one example of a method of bending a long length of the member and a bending apparatus for use in such method.

[0029] First, a bending apparatus for a long length of a member A will be described. The bending apparatus for the long length of the member A includes an outer forming assembly 6 and an inner forming assembly 20. Referring to the outer forming assembly 6, FIG. 2 shows the whole view of the outer forming assembly 6 and FIGS. 2(a) is a top plan view, (b) is a sectional front elevation view and (c) is a sectional side elevation view. The outer forming assembly 6 has a base 7, sidewalls 8, a forming pad 9 and die plates 10. The base 7 is approximately rectangular and has a grove 11 extending in the longitudinal direction at the midsection thereof. A pair of sidewalls 8 opposed to each other is provided in the groove 11. The sidewalls 8 are approximately in forms of a landscape rectangular plate, placed and held on a bottom surface of the groove 11 to be installed in a standing manner in the transverse direction of the groove 11 and arranged in such a way that outer side faces of respective sidewalls 8 abut against inner side faces of the groove 11. The sidewalls 8 are installed in such a way that the height thereof becomes nearly equal to the height of the side faces of the groove 11.

[0030] A rectangular cavity 12 extending upward is provided at the midsection of a bottom face of the groove 11 between the sidewalls 8. The forming pad 9 is inserted movably up and down into the rectangular cavity 12. The die plates 10 are installed on both sides of the forming pad 9. Gaps 13 are provided between the sidewall 8 and the forming pad 9 and between the sidewall 8 and the die plate 10. The gaps 13 are provided for the sidewalls 8 to move. The die plates 10 are supported by pins 14 on the outer sides relative to the base 7 and installed rotatably up and down on the inner sides. There is the following relation between the forming pad 9 and the die plates 10 described above. That is, the forming pad 9 has inclined portions 15 inclined downward on the sides of respective die plates 10 and respective tips of the inner sides of the die plates 10 are placed and held on the inclined portion 15. Therefore, there is the relation that the forming pad 9 sides of the die plates 10 rotate up and down following up-and-down movements of the forming pad 9. Further, a spring 16 is installed at a bottom face of the forming pad 9, and the forming pad 9 is applied with a force upward. Accordingly, the die plates 10 placed and held on the inclined portion 15 of the forming pad 9 become a state that the inner sides of the die plates 10 is rotated upward since the forming pad 9 sides project upward, and bottom faces of the die plates 10 and a top face of the base 7 are in the condition of not contacting. Further, a top face of the forming pad 9 and top faces of the die plates 10 are installed so as to be lower than the height of the sidewalls 8.

[0031]FIG. 3 shows the whole view of the inner forming assembly 20 and FIGS. 3(a) is a bottom plan view, (b) is a front elevation view and (c) is a sectional side elevation view. The inner forming assembly 20 has a base 21, a punch 22 and wedge plates 23. The base 21 is approximately rectangular and the punch 22 is attached to a bottom face thereof and a pair of wedge plates 23, 23 are installed on both sides of the punch 22. The punch 22 has a configuration of which a midsection projects downward like a mountain, and tip portion thereof forms an inner shape of the long length of the member A. Respective wedge plates 23 are approximately in forms of a landscape rectangular plate and includes the wedge portion 23 a located at a front-end thereof and a restraining portion 23 b located above the wedge portion. The wedge plates 23 are attached to a bottom face of the base 7 so as to be vertical downward in the direction of the plate thickness. When the inner forming assembly 20 is fitted into the outer forming assembly 6, the punch 22 is inserted between the sidewalls 8 of the outer forming assembly 6. The punch 22 abuts against the top face of the forming pad 9 installed between the sidewalls 8 and the forming pad 9 is lowered by pressing force of the punch 22. As the forming pad 9 is lowered, the inner end sides of the die plates 10 are rotated downward and a bottom face of the die plates 10 abuts against a top face of a base 7 at the lowest end the forming pad 9. In this time, the top face of the forming pad 9 and the top face of the die plate 10 are installed so as to form an outer shape of the long length of the member A. That is the top face of the forming pad 9 has a concave portion for largely bending in the longitudinal direction and the top face of the die plate 10 has a concave portion for small bending in the longitudinal direction.

[0032] Here, a moving mechanism for the sidewalls 8 will be illustrated. Vertical grooves 17, which are approximately U-shaped in cross section, extending vertically are formed beside the groove 11 of the outer forming assembly 6. The vertical grooves 17 are provided to insert the wedge plates 23 installed to the inner forming assembly 20 into it. On the other hand, tip thickness of the wedge portion 23 a of the wedge plate 23 installed to the inner forming assembly 20 is set to a dimension smaller than the depth of the vertical groove 17 and thickness of the restraining portion 23 b is set to a dimension larger than the depth of the vertical groove 17. Further, the difference between the thickness of the restraining portion 23 b of the wedge plate 23 and the depth of the vertical groove 17 is set so as to become nearly equal to the width of a gap 13 provided between the sidewall 8 and the forming pad 9 and between the sidewall 8 and the die plate 10.

[0033] When the inner forming assembly 20 is lowered together with the start of the bending, the wedge plates 23, respectively, installed to the inner forming assembly 20 are inserted into the vertical groove 17 provided in the outer forming assembly 6. When the wedge portions 23 a of the wedge plates 23 are inserted into the vertical groove 17 to some extent, the wedge portions 23 a abut against a bottom face of the vertical groove 17 and side faces of sidewalls 8. And so, the sidewalls 8, placed and held on a bottom surface of the groove 11 of a top face of the base 7 and not secured, move inside gradually.

[0034] Next, a method of bending the long length of the member A will be described. FIGS. 4 to 8 show sectional diagrammatic sketches representing in stages the bending of the long length of the member A. In each drawing, drawing number (a) indicates a sectional front elevation view and (b) indicates a sectional side elevation view. First, the long length of the member A formed to have a predetermined shape in transverse cross section is carried between the sidewalls 8 of the outer forming assembly 6 with the free end sides of flanges 2 up and set on the top faces of the forming pad 9 and the die plates 10 installed between the sidewalls 8. In this time, the sidewalls 8 position on the outer sides, the forming pad 9 is applied with a force upward by a spring 16 provided at the bottom face of the forming pad 9 and the inner sides of the die plates 10 are rotated upward following the forming pad 9.

[0035] By lowering the inner forming assembly 20, the wedge portions 23 a of the wedge plates 23 installed to the inner forming assembly 20 are inserted into the vertical groove 17 provided in the outer forming assembly 6. When the wedge portions 23 a of the wedge plates 23 are inserted into the vertical groove 17 by the specified depth, the wedge portions 23 a abut against the bottom face of the vertical groove 17 and the side faces of sidewalls 8. On the other hand, the sidewalls 8 are placed and held on a bottom surface of the groove 11 provided on the top face of the base 7 of the outer forming assembly 6 and are not secured. Therefore, the sidewalls 8 are pressed by the wedge portions 23 a to move inside (FIG. 4). And, by lowering the inner forming assembly 20 further, the restraining portions 23 b of the wedge plates 23 installed to the inner forming assembly 20 are inserted into the vertical groove 17 of the outer forming assembly 6, and the side faces of the sidewalls 8 are pressed against the side faces of the forming pad 9 and the die plates 10.

[0036] On the other hand, the punch 22 attached to the inner forming assembly 20 is inserted between the sidewalls 8 of the outer forming assembly 6 and a tip of the punch 22 is impacted into the inside of the long length of the member A. By pressing a part to be a largely bending part 3 of the platelike bottom portion 1 of the long length of the member A by the punch 22, the long length of the member A is bent as a bending fulcrum of both sides of a concave portion for largely bending of a top face of the forming pad 9. And, the forming pad 9 is lowered and the sides of the forming pad 9 of the die plates 10 are rotated downward following a descent of the forming pad 9 by pressing force of the punch 22 (FIG. 5). When the inner forming assembly 20 is lowered further, by pressing a part to be a largely bending part 3 of the platelike bottom portion 1 of the long length of the member A by a tip of the punch 22 keeping the sidewall 8 restrained, the forming pad 9 is lowered further and the die plates 10 are rotated downward. Thereby, a bending fulcrum of the long length of the member A is extended from both sides of a concave portion for largely bending of a top face of the forming pad 9 to the sides of the die plates 10 depending on bending in the longitudinal direction and a largely bending part 3 of the long length of the member A is formed gradually.

[0037] The deformation that free end sides of flanges 2 shrink and platelike bottom portion 1 sides of the flanges 2 expand in the longitudinal direction of the long length of the member is produced by this bending, and the wrinkles are going to be produced gradually at flanges 2. However, since respective flanges 2 are pressed against side faces of the punch 22 by side faces of the sidewalls 8, the occurrence of wrinkles will be restrained (FIG. 6).

[0038] When the inner forming assembly 20 is lowered further, the tip of the punch 22 presses the platelike bottom portion 1 of the long length of the member A further while side faces of the sidewalls 8 press respective flanges 2 against side faces of the punch 22, the forming pad 9 is lowered and the die plates 10 are rotated downward. Therefore, the bending fulcrum of the long length of the member A is extended to both sides of the long length of the member A. By this bending, and the wrinkles are going to be produced newly at flanges 2. However, since respective flanges 2 are pressed against the side faces of the punch 22 by the side faces of the sidewalls 8, the occurrence of wrinkles will be restrained (FIG. 7).

[0039] Here, as the forming pad 9 is lowered, the ironing is applied to each flange 2 of the long length of the member A through the side faces of the sidewall 8 and the side faces of the punch 22. As the forming pad 9 is lowered, the sides of the forming pad 9 of the die plates 10 are rotated downward, and therefore the flanges 2 applied with the ironing is extended gradually toward both ends of the long length of the member A and this results in the ironing of the whole flange 2. Therefore, it is possible to restrain the occurrence of wrinkles further.

[0040] When the inner forming assembly 20 is lowered further, the tip of the punch 22 presses the part to be the largely bending part 3 of the platelike bottom portion 1 of the long length of the member A while the side faces of the sidewalls 8 press the respective flanges 2 against side faces of the punch 22, the forming pad 9 reaches at the lowest end and a bottom face of the die plates 10 abuts against a top face of a base 7. In this time, a top face of the forming pad 9 and a top face of the die plate 10 form an outer shape of the long length of the member A and the long length of the member A is forcedly pressed against the top face of the forming pad 9 and the top face of the die plate 10 by the punch 22. Thereby, the long length of the member A is pressed against a concave portion for largely bending provided on the top face of the forming pad 9 and a concave portion for small bending provided on the top face of the die plate 10, and therefore a largely bending part 3 and a small bending part of the long length of the member A are formed in the longitudinal direction and the bending of the long length of the member A is completed (FIG. 8).

[0041] After the completion of the bending, the inner forming assembly 20 is raised, the punch 22 is drawn from between the sidewalls 8 and the wedge plates 23 are drawn from the vertical groove 17. Accordingly, the sidewall 8 are freed from the constraints of the wedge plates 23 and the distance between the sidewalls 8 is expanded outward of itself. Since the distance between the sidewalls 8 is expanded, the long length of the member A may be taken out from the outer forming assembly 6 easily after the completion of the bending.

[0042] In accordance with the above-mentioned method of bending a long length of a member A and the above-mentioned bending apparatus for a long length of a member A, it is possible to restrain the occurrence of wrinkles effectively, which are going to be produced at flanges 2 due to bending the long length of the member A. That is, by pressing a largely bending part 3 of the platelike bottom portion 1 of the long length of the member A by the punch 22 provided in the inner forming assembly 20, the deformation that free end sides of flanges 2 shrink and platelike bottom portion 1 sides of the flanges 2 expand is produced in the longitudinal direction of the long length of the member A. The wrinkles are going to be produced at flanges 2 due to the deformation. However, since a side face of the sidewalls 8 press respective flanges 2 against a side face of the punch 22, and the side face of the sidewall 8 and the side face of the punch 22 do the ironing of the flanges 2, it is possible to restrain the occurrence of wrinkles.

[0043] And, in the outer forming assembly 6, the forming pad 9 is applied with a force upward by a spring 16, a means for applying a force, provided at the bottom face and the die plates 10 supported by pins 14 are installed on both sides of the forming pad 9. The die plates 10 are placed and held on an inclined portion 15 provided on the forming pad 9 at a tip of the bottom face thereof and installed rotatably following up-and-down movements of the forming pad 9. Therefore, by pressing a part to be a largely bending part 3 of the platelike bottom portion 1 of the long length of the member A by the punch 22 installed in the inner forming assembly 20, the forming pad 9 is lowered and the sides of the forming pad 9 of the die plates 10 are rotated downward, and a bending fulcrum of the long length of the member A is extended gradually toward both ends of the long length of the member A and a largely bending part 3 is formed gradually. Thereby, since free end sides of the flanges 2 of the largely bending part 3 shrink gradually, it is possible to prevent the occurrence of buckling of the flanges 2 effectively.

[0044] Here, as the forming pad 9 is lowered, the ironing is applied to each flange 2 of the long length of the member A through the side faces of the sidewall 8 and the side faces of the punch 22. As the forming pad 9 is lowered, the sides of the forming pad 9 of the die plates 10 are rotated downward, and therefore the flanges 2 applied with the ironing is extended gradually toward both ends of the long length of the member A and this results in the ironing of the whole flange 2, and so it is possible to restrain the occurrence of wrinkles further.

[0045] Further, each sidewall 8 provided in the outer forming assembly 6 has a moving mechanism for moving inside. Therefore, when the long length of the member A is set to the outer forming assembly 6, the long length of the member A may be set to the outer forming assembly 6 easily since the sidewalls 8 position on outer sides, and when bending, the punch 22 is inserted between the sidewalls 8 and the sidewalls 8 are moved to inner sides by the wedge plates 23 and abut 2 against the flanges 2, and bending is carried out while doing the ironing of the flanges 2 with the side faces of the sidewalls 8 and the side faces of the punch 22, and after bending is completed, the punch 22 is drawn from between the sidewalls 8 and the wedge plates 23 are drawn from the vertical groove 17, and the sidewalls 8 are freed from the constraints of the wedge plates 23 and move so as to expand the distance between the sidewalls 8 outward of itself. According, the long length of the member A may be taken out from the outer forming assembly 6 easily. 

What is claimed is:
 1. A method of bending a long length of a member, wherein, in a long length of a member having a platelike bottom portion (1) and flanges (2) installed in a standing manner at the end of the platelike bottom portion (1), free end sides of the flanges (2) shrink and platelike bottom portion (1) sides of the flanges (2) expand, characterized in that, in bending the long length of the member by using an inner forming assembly (20) forming an inner bent shape of the long length of the member and an outer forming assembly (6) forming an outer bent shape of the long length of the member and by pressing the platelike bottom portion (1) in said outer forming assembly (6) with said inner forming assembly (20), said flanges (2) are pressed from both sides thereof between a sidewall (8) of said outer forming assembly (6) and said inner forming assembly (20), respectively, and bending is carried out while doing the ironing of said flanges (2) with said sidewall (8) and said inner forming assembly (20).
 2. A bending apparatus for a long length of a member for carrying out the bending in which, in a long length of a member having a platelike bottom portion (1) and flanges (2) installed in a standing manner at the end of the platelike bottom portion (1), free end sides of the flanges (2) shrink and platelike bottom portion (1) sides of the flanges (2) expand, including an inner forming assembly (20) forming an inner bent shape of the long length of the member and an outer forming assembly (6) forming an outer bent shape of the long length of the member, bending the long length of the member by pressing the platelike bottom portion (1) in said outer forming assembly (6) with said inner forming assembly (20), characterized in that said flanges (2) are pressed from both sides thereof between a sidewall (8) provided in said outer forming assembly (6) and said inner forming assembly (20), respectively, and the bending is carried out so as to do the ironing of said flanges (2) with said sidewall (8) and said inner forming assembly (20).
 3. The bending apparatus for a long length of a member as set forth in claim 2, the bending apparatus having a forming pad (9) ad die plates (10) in the longitudinal direction in such a way that said outer forming assembly (6) forms an outer bent shape of the long length of the member, characterized in that said forming pad 9 is installed so as to be capable of projecting and retracting by being applied with a force toward the direction of said inner forming assembly (20) by a means (16) of applying a force and the sides of said forming pad (9) of said die plates (10) are installed rotatably following a projection/retraction of said forming pad (9).
 4. The bending apparatus for a long length of a member as set forth in either claim 2 or claim 3, characterized in that the bending apparatus have a moving mechanism for moving said sidewalls (8) away from said flanges (2). 